1. Field of the Invention
This disclosure relates to an illuminating apparatus, a backlight assembly and a liquid crystal display device having the same, more particularly, to an illuminating apparatus providing an enhanced brightness, a backlight assembly and a liquid crystal display device having the same.
2. Description of the Related Art
Electronic display devices have been important as information transmission medias, and various electronic display devices are widely applied in industrial devices and home appliances. Such electronic display devices have been continuously improved to have new functions appropriate for various demands of users.
In general, electronic display devices display and transmit various information to users. That is, the electronic display devices convert electric information signals into light information signals capable of being recognized by users.
Electronic display devices may be categorized into emissive type display devices and non-emissive type display devices. The emissive type display devices may include a cathode ray tube (“CRT”), a plasma display panel (“PDP”), a light emitting diode (“LED”) and/or an electro luminescent display (“ELD”), for example. The emissive display type devices are also called active display devices. The non-emissive display devices, which are also called passive display devices, may include a liquid crystal display (“LCD”) device, an electrochemical display (“ECD”) and/or an electrophoretic image display (“EPID”), for example.
Flat plate type display devices have lighter weight and smaller size, in comparison with the CRT, and various flat plate type display devices have been developed to provide full-color, high resolution and the like.
In LCD devices, as a representative of the flat plate type display devices, an electric field is applied to liquid crystal molecules, and an alignment of the liquid crystal molecule is changed depending on the electric field, to thereby change optical properties of the liquid crystal, such as double refraction, optical rotatory power, dichroism, light scattering, etc. The LCD devices display images by using the changes of the optical properties of the liquid crystal.
As mentioned above, the LCD devices are non-emissive type display devices, so that the LCD devices display images by reflecting the external light transmitted through an LCD panel or by using the light emitted from a light source, e.g. a backlight assembly, disposed below the LCD panel.
This backlight assembly includes a lamp unit for emitting light, a light guiding plate (“LGP”) for guiding the light emitted from the lamp unit toward the LCD panel, a reflecting plate (or a reflector) disposed under the light guiding plate so as to reflect the lights leaked from the light guiding plate toward the light guiding plate, and optical sheets for enhancing brightness of the light exited from the light guiding plate.
In general, the backlight assembly may be categorized into a flat type backlight assembly having lamp units at both sides of the light guiding plate and a wedge type backlight assembly having a lamp unit (lamp units) at one side of the light guiding plate, depending upon locations of the lamp units with respect to the light guiding plate.
FIG. 1 is a sectional view showing a conventional flat type backlight assembly.
Referring to FIG. 1, the flat type backlight assembly includes lamp reflectors 12a and 12b, lamp units 14a and 14b, and a reflection plate 18. The lamp reflectors 12a and 12b are disposed on both sides of a light guiding plate 10, and the lamp units 14a and 14b are received in the lamp reflectors 12a and 12b. The light guiding plate 10 guides the light emitted from the lamp units 14a and 14b toward a diffusion sheet 16, and the lamp reflectors 12a and 12b prevent the light emitted from the lamp units 14a and 14b from being leaked from the backlight assembly. The reflection plate 18 reflects the light leaked from the light guiding plate 10 toward the light guiding plate 10.
The light guiding plate 10 installed in the backlight assembly is comprised of a high polymer, e.g. polymethyl methacrylate (“PMMA”) or cyclic olefin polymer (“COP”), so that the light guiding plate 10 is the heaviest element of the elements in an LCD module. Accordingly, the wedge type backlight assembly may be proper for an LCD device of a lap top computer, in which a lighter weight and a slimmer size are important factors, rather than the flat type backlight assembly.
FIG. 2 is a sectional view showing a conventional wedge type backlight assembly.
Referring to FIG. 2, the wedge type backlight assembly includes a lamp reflector 22 and a lamp unit 24. A light guiding plate 20 guides the light emitted from the lamp unit 24 toward a diffusion sheet 26. The lamp reflector 22 is disposed on one side of the light guiding plate 20, and prevents the light emitted from the lamp unit 24 from being leaked from the lamp unit 24. The lamp unit 24 is disposed in the lamp reflector 22. The backlight assembly further includes a reflecting plate 28 disposed under the light guiding plate 20 for reflecting the light leaked from a lower surface of the light guiding plate 20.
However, there is a limit in enhancing brightness of the backlight assembly when the backlight assembly employs a lamp reflector that provides specular reflection property.